(defun rwd-sudo-buffer ()
  "Revert buffer using tramp sudo.
    This will also reserve changes already made by a non-root user."
  (interactive)
  (let ((f (buffer-file-name)))
    (when f
      (let ((content (when (buffer-modified-p)
                       (widen)
                       (buffer-string))))
        (if (file-writable-p f)
            (revert-buffer)
          (kill-buffer (current-buffer))
          (find-file (concat "/sudo::" f))
          (when content
            (let ((buffer-read-only nil))
              (erase-buffer)
              (insert content))))))))